Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

743
FXUS63 KLOT 311728
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1128 AM CST Sat Jan 31 2026

.KEY MESSAGES...

- Lake effect snow will continue across northeastern Illinois
  and far northwest Indiana today, with the potential for
  localized amounts of a few inches of new accumulation and
  travel impacts along the Lake Michigan shore.

- There may be a period of light snow accumulations Sunday
  night into Monday, followed by less cold conditions by
  midweek.

&&

.UPDATE...
Issued at 1024 AM CST Sat Jan 31 2026

The primary north-to-south oriented lake induced boundary layer
convergence axis (main focus for lake effect snow showers)
remains anchored along the southwestern part of Lake Michigan
early this morning. This roughly resides, from a few miles
offshore of Chicago southward into Lake county IN. This axis
will continue to be primary focus for potentially more
substantial lake effect snow showers into this afternoon as it
gradually shifts a bit farther to the west towards the Cook
county shoreline. In recent hours, however, AMDAR soundings
have indicated the presence of directional shear in the
convective layer. This has proved detrimental to the continued
organization of the primary lake effect band, as a more
widespread area of low impact flurries and light snow showers
has evolved across much of northeastern IL into northwestern IN
thus far this morning. This thus adds some questions as to if
the going Winter Weather Advisory will be needed into this
afternoon.

For the time being we are not planning to end the Winter
Weather Advisory early, as it remains possible that band
organization could improve for a period this afternoon as
directional shear decreases. Confidence on this remains low at
this time, especially considering lake induced thermodynamics
will only remain modest at best. If the band begins to become a
bit more organized early this afternoon, there would be a
higher potential for at least some localized higher snow rates
and amounts near the lake in Cook county. Otherwise,
accumulations would be likely to remain under an inch with
little in the way of impacts. We will continue to monitor trends
over the next few hours.

Otherwise, expect the threat of these lake effect snow showers
to come to an end this evening.

KJB

&&

.DISCUSSION...
Issued at 331 AM CST Sat Jan 31 2026

Our reprieve from lake effect snow (LES) has been short-lived,
as another prominent LES band on a low-level trough axis is
working southwestward toward the Illinois and Indiana shores
early this morning. This surface trough is expected to sharpen a
low-level convergence axis along the Illinois shore and into
far northwest Indiana this morning before drifting east and
weakening this afternoon and early evening.

Unlike on Friday, the low-level flow should become more steady-
state and allow and LES to remain more-or-less in the same
vicinity for several hours. There remains only medium confidence
on exactly where this band sets up, with the growing amount of
lakeshore ice becoming a major wildcard. While some CAMs favor
placing the main band solidly in Cook County, the amount of
shore ice suggests that the band will anchor on or possibly
slightly east of the shore.

Though inversion heights have lowered to around 5-6kft, much of
the convective cloud depths remain in the DGZ. This should push
SLR values at or above 20:1 within any focused band. So when
all is said and done this morning into the afternoon, snowfall
amounts of 2 to 4 inches appear likely under the band, with
localized higher amounts of 6 inches. Whether those highest
totals are realized over land (including downtown Chicago) or
just offshore remains unclear. Much of the snow should fall
through early afternoon, with snowfall rates over 1 inch per
hour or higher under then main band this morning.

Headlines: The only minor change to the Cook and eastern Will
County Winter Weather Advisories was to move up the start time
to 5am for the earlier arrival of the initial lake band. As for
northwest Indiana, opted to end the Winter Storm Warning in
favor of an advisory given the lower totals and observed break
from earlier heavy snow last evening.

Otherwise away from the LES, subtle ascent within the entrance
of a weak mid-level speed max is allowing for an area of higher
low-level moisture with the DGZ to produce light snow.
Expectations are for periods of light snow showers or flurries
to persist over much of the area through the morning.

Backing low-level flow and lowering inversion heights will end
any remaining LES in northwest Indiana by late evening. A
clipper like system will pass north of the area late Sunday into
Monday morning, with an increasing chance of low-level WAA-
induced light snow with accumulations under an inch Sunday
night.

Overall northwest flow will persist through the upcoming week,
though the coldest airmasses should stay well northeast of the
area. Ensemble guidance continues to keep a stronger storm
system to the south (over the Ohio and Tennessee Valleys) while
another, albeit weaker, period of LES is possible into northwest
Indiana and northeast Illinois Tuesday night into Wednesday
morning.

Kluber

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1128 AM CST Sat Jan 31 2026

Key messages for the 18Z TAF period:

* Intermittent (mostly) light snow showers continuing at ORD,
  MDW, and GYY into this afternoon

* MVFR expected through at least mid-late afternoon, if not beyond

The lake effect snow band has largely lightened up for the
morning, but still seeing steady light snow showers move over
MDW and GYY with the occasional pocket of moderate snow. Brief
bouts of MVFR snow will remain possible at MDW through mid-
afternoon and at GYY through late afternoon. Flurries or the
occasional light snow shower may still move over ORD into early
afternoon.

There is a signal for a return to VFR at the Chicago sites by
mid-late afternoon (likely later at MDW), although confidence
is rather low and MVFR may remain into this evening. GYY may not
see a return to VFR until late tonight, if not after daybreak.

Meanwhile, NNW winds between 10 and 20 kt will continue through
the afternoon before lightening up and going SW late tonight.
Expect SW winds at 10 to 20 kt by end of morning Sunday.

Doom

&&

.HYDROLOGY...
Issued at 230 PM CST Wed Jan 28 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until 4 PM CST this afternoon for
     ILZ103-ILZ104-ILZ105-ILZ108.

IN...Winter Weather Advisory until 6 PM CST this evening for INZ001.

     Winter Weather Advisory until noon CST today for INZ002.

LM...Small Craft Advisory until 2 PM CST this afternoon for the IL
     and IN nearshore waters.

&&

$$

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